Double seal thermostat

Abstract

A choke type thermostat is provided with dual choke seals including a conventional primary choke and a secondary choke which seals with the valve seat of the thermostat prior to the sealing of the primary choke. The secondary choke provides additional sealing for the valve and also functions to strain the flow of coolant which is allowed to pass over the primary choke, thereby preventing sand or other debris from interfering with the sealing of the primary choke.

What is claimed is: 
     
       1. A choke type double seal thermostat comprising: a circular valve body having an outer flange adapted for mounting in an engine and a valve seat tapered in the axial direction toward the axis of said of said valve body;   a thermoelongating valve pin disposed on the axis of said valve body, said valve body having means to retain a first end of said valve pin thereagainst;   a primary valve choke of cup-shaped configuration fixably attached to said valve pin, said primary valve choke having an open end defining a circular axial edge disposed to gradually move axially and independently of the pressure differential across the valve seat into sealing contact with said tapered valve seat;   a valve spring disposed between said first cylindrical valve choke and said valve pin to bias said first valve choke against said valve seat;   a secondary valve choke comprising a metallic cylinder axially slidably disposed concentrically adjacent the periphery of said primary valve choke, said secondary valve choke having a circular axial edge disposed in first spring biased position of said secondary valve choke to make, upon axial movement of said primary choke toward said valve seat, sealing contact with said valve seat prior to said primary choke contacting said valve seat; and   a secondary choke compression spring operatively disposed between said primary valve choke and said secondary valve choke to bias said secondary valve choke to said spring biased position, said secondary choke spring being substantially smaller than said valve spring such that, upon said primary valve choke moving toward said valve seat, said secondary valve choke telescopingly retracts upon contact with said valve seat until said primary valve choke engages said valve seat.   
     
     
       2. The invention in accordance with claim 1 and said primary and secondary valve chokes having interengaging stop means disposed thereon for limiting the travel of said secondary choke to said first spring biased position.